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Diffstat (limited to 'doc/manual/src/expressions/expression-syntax.md')
| -rw-r--r-- | doc/manual/src/expressions/expression-syntax.md | 66 |
1 files changed, 33 insertions, 33 deletions
diff --git a/doc/manual/src/expressions/expression-syntax.md b/doc/manual/src/expressions/expression-syntax.md index e3432b577..2a1306e32 100644 --- a/doc/manual/src/expressions/expression-syntax.md +++ b/doc/manual/src/expressions/expression-syntax.md @@ -2,17 +2,19 @@ Here is a Nix expression for GNU Hello: - { stdenv, fetchurl, perl }: ① - - stdenv.mkDerivation { ② - name = "hello-2.1.1"; ③ - builder = ./builder.sh; ④ - src = fetchurl { ⑤ - url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz"; - sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465"; - }; - inherit perl; ⑥ - } +```nix +{ stdenv, fetchurl, perl }: ① + +stdenv.mkDerivation { ② + name = "hello-2.1.1"; ③ + builder = ./builder.sh; ④ + src = fetchurl { ⑤ + url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz"; + sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465"; + }; + inherit perl; ⑥ +} +``` This file is actually already in the Nix Packages collection in `pkgs/applications/misc/hello/ex-1/default.nix`. It is customary to @@ -31,31 +33,27 @@ elements (referenced from the figure by number): etc. `fetchurl` is a function that downloads files. `perl` is the Perl interpreter. - Nix functions generally have the form `{ x, y, ..., - z }: e` where `x`, `y`, etc. are the names of the expected - arguments, and where *e* is the body of the function. So here, the - entire remainder of the file is the body of the function; when given - the required arguments, the body should describe how to build an - instance of the Hello package. + Nix functions generally have the form `{ x, y, ..., z }: e` where + `x`, `y`, etc. are the names of the expected arguments, and where + *e* is the body of the function. So here, the entire remainder of + the file is the body of the function; when given the required + arguments, the body should describe how to build an instance of + the Hello package. 2. So we have to build a package. Building something from other stuff is called a *derivation* in Nix (as opposed to sources, which are built by humans instead of computers). We perform a derivation by - calling `stdenv.mkDerivation`. `mkDerivation` is a function provided - by `stdenv` that builds a package from a set of *attributes*. A set - is just a list of key/value pairs where each key is a string and - each value is an arbitrary Nix expression. They take the general - form `{ - name1 = - expr1; ... - nameN = - exprN; }`. + calling `stdenv.mkDerivation`. `mkDerivation` is a function + provided by `stdenv` that builds a package from a set of + *attributes*. A set is just a list of key/value pairs where each + key is a string and each value is an arbitrary Nix + expression. They take the general form `{ name1 = expr1; ... + nameN = exprN; }`. -3. The attribute `name` specifies the symbolic name and version of the - package. Nix doesn't really care about these things, but they are - used by for instance `nix-env - -q` to show a “human-readable” name for packages. This attribute is - required by `mkDerivation`. +3. The attribute `name` specifies the symbolic name and version of + the package. Nix doesn't really care about these things, but they + are used by for instance `nix-env -q` to show a “human-readable” + name for packages. This attribute is required by `mkDerivation`. 4. The attribute `builder` specifies the builder. This attribute can sometimes be omitted, in which case `mkDerivation` will fill in a @@ -83,8 +81,10 @@ elements (referenced from the figure by number): `perl` function argument to the builder. All attributes in the set are actually passed as environment variables to the builder, so declaring an attribute - - perl = perl; + + ```nix + perl = perl; + ``` will do the trick: it binds an attribute `perl` to the function argument which also happens to be called `perl`. However, it looks a |